// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#nullable disable

using System.Security.Cryptography;
using System.Text.Encodings.Web;
using System.Text.Json;
using Microsoft.Build.Framework;

namespace Microsoft.AspNetCore.StaticWebAssets.Tasks;

public class GenerateJSModuleManifest : Task
{
    private static readonly JsonSerializerOptions ManifestSerializationOptions = new()
    {
        Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
        WriteIndented = true
    };

    [Required]
    public string OutputFile { get; set; }

    [Required]
    public ITaskItem[] JsModules { get; set; }

    public override bool Execute()
    {
        var modules = StaticWebAssetEndpoint.FromItemGroup(JsModules).Select(s => s.Route).ToArray();
        Array.Sort(modules, StringComparer.Ordinal);

        PersistModules(modules);
        return !Log.HasLoggedErrors;
    }

    private void PersistModules(string[] modules)
    {
        var data = JsonSerializer.SerializeToUtf8Bytes(modules, ManifestSerializationOptions);
#if !NET9_0_OR_GREATER
        using var sha256 = SHA256.Create();
        var currentHash = sha256.ComputeHash(data);
#else
        var currentHash = SHA256.HashData(data);
#endif
        Directory.CreateDirectory(Path.GetDirectoryName(OutputFile));

        var fileExists = File.Exists(OutputFile);
        var existingManifestHash = fileExists ?
#if !NET9_0_OR_GREATER
            sha256.ComputeHash(File.ReadAllBytes(OutputFile)) :
#else
            SHA256.HashData(File.ReadAllBytes(OutputFile)) :
#endif
            [];

        if (!fileExists)
        {
            Log.LogMessage(MessageImportance.Low, $"Creating manifest because manifest file '{OutputFile}' does not exist.");
            File.WriteAllBytes(OutputFile, data);
        }
        else if (!currentHash.SequenceEqual(existingManifestHash))
        {
            Log.LogMessage(MessageImportance.Low, $"Updating manifest because manifest version '{Convert.ToBase64String(currentHash)}' is different from existing manifest hash '{Convert.ToBase64String(existingManifestHash)}'.");
            File.WriteAllBytes(OutputFile, data);
        }
        else
        {
            Log.LogMessage(MessageImportance.Low, $"Skipping manifest updated because manifest version '{Convert.ToBase64String(currentHash)}' has not changed.");
        }
    }
}